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Response to [Affordance, conventions, and design] by Norman

One Sentence

This article discussed how ‘affordance’ is misused in user interface design and what really play an important role is ‘constraint’ and ‘convention’.

More Sentence & Key Points

  • Affordance
    Specifically, affordance refers to a set of possible actionables between a person and an object; it suggest what might be done by the person to that object.
    Real affordance is intrinsic and inherent; perceived affordance is generated from the person’s understanding.
    More definitions or descriptions:
    •  (Affordance by J. J. Gibson) …refer to the actionable properties between the world and an actor (a person or animal). To Gibson, affordances are relationships. They exist naturally; they do not have to be visible, known, or desirable.
    • Affordances specify the range of possible activities, but affordances are of little use if they are not visible to the users. Hence, the art of the designer is to ensure that the desired, relevant actions are readily perceivable.
    • Affordances reflect the possible relationships among actors and objects: they are properties of the world. (Conventions, conversely, are arbitrary, artificial, and learned.)
  • Constraints
    In the private conversation between a user and an interface, constraints refer to a set of factors that are pertinent to the interface, and that induce the user’s behavior.
    • Physical constraints: closely related to real affordances; make some actions impossible, e.g., can’t move the cursor out of the screen;
    • Logical constraints: use reasoning to determine the alternatives, e.g., edit information, page remains the same, know a refresh is needed.
    • Cultural constraints: conventions shared by a cultural group, e.g., the slider for scrolling a web page is very likely to be on the right or bottom.
  • Conventions== Cultural constraints
    • When designing a graphical screen layout, designers greatly rely on conventional interpretations of the symbols and placement. Much of the discussion about the use of affordances is really addressing conventions, or what I call cultrual constraints.
    • A convention is a cultural constraint, one that has evolved over time.


  • In short, affordance isn’t really relevant to a computer interface; what really matters is constraint, and what really helps the design is cultural constraint (convention).
  • I really want to see a similar discussion, not based on GUI, but in the backdrop of Ubicomp. When computing migrates to the real world, will the definition of affordance embrace computer interface? Will it be different?

About Xiang 'Anthony' Chen

Making an Impact in Your Life


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